big_o_palindrome.js

// By Alex https://github.com/AlexVotry
// reverse the string
  // temp variable
  // split - turns the string into an array
  // reverse - built in function on array
  // join - turns an array into a string with a given delimiter ''
// compare to original string
// if equal return True else return false


// By Devany https://github.com/devanymoe
// recursion!!

// BASE CASE
// length 1 - last char - is a palindrome
// length 2 - last 2 equal - then palindrome

// compare first and last letter
// if equal
  // remove first and last letter from array
  // DO IT AGAIN!
// if not
  // not a palindrome


  /* Created by David Adams December 02 2015
https://github.com/gSchool/DailyProgrammer/blob/master/03_palindrome/solutions/DTA.js
  */
  function palindrome(phrase) {
    phrase = sanitize(phrase);
    if (phrase[0] != phrase[phrase.length - 1]) {
      return false;
    }
    return phrase === reverse(phrase);
  }

  // Total: O(n + n + n) = O(n)
  function reverse(string) {
    // split - O(n)
    // reverse - O(n)
    // split - O(n)
    return join.split('').reverse().join('');
    /* another way to reverse - more efficient */
    // O(n)
    // var revString = '';
    // for (var i = string.length - 1; i >=0; i--) {
    //   revString += string[i];
    // }
    // return revString;
  }

  // Total: O(n + n) = O(n)
  function sanitize(string) {

    // split - O(n)
    // split - O(n)
    return string.toLowerCase().replace(/\s/g, '');
  }

// Big O
O(n) + O(n) + O(n) + O(n) + O(n)
O(5 * n) = O(n)

console.log(palindrome("poop"));
console.log(palindrome("Alula"));
console.log(palindrome("A but tuba"));
console.log(palindrome("Not a palindrome"));